Abstract Nutrient recycling is fundamental to sustainable agricultural systems, but few mechanisms exist to ensure that surplus manure nutrients from animal feeding operations are transported for use on nutrient-deficient croplands. As a result, manure nutrients concentrate in locations where they can threaten environmental health and devalue manure as a fertilizer resource. This study advances the concept of the “manureshed” – the lands surrounding animal feeding operations onto which manure nutrients can be redistributed to meet environmental, production, and economic goals. Manuresheds can be managed at multiple scales, for example, on farms with both animals and crops, among animal farms and crop farms within a county, or even among animal farms and crop farms in distant counties. With a focus on redistribution among counties, we classified the 3109 counties of the contiguous United States by their capacity to either supply manure phosphorus (P) and nitrogen (N) from confined livestock production (“sources”) or to assimilate and remove excess P and N via crops (“sinks”). Manure nutrient source counties were identified in 40 of the 48 states, with a substantial concentration in the southern US. Source counties for manure P greatly outnumbered source counties for manure N (390 vs. 100), and 99 of the 100 manure N source counties were also source counties for manure P. Conversely, sink counties for manure N outnumbered sink counties for manure P (2766 vs. 2317). We used the P balances of the source and sink counties to delineate four manuresheds dominated by various combinations of confined hog, poultry, dairy, and beef industries. The four manuresheds differed in the transport distances needed to assimilate excess manure P from their respective source areas (from 147 ± 51 km for a beef dominated manureshed to 368 ± 140 km for a poultry dominated manureshed), highlighting the need for systems-level strategies to promote manure nutrient recycling that operate across local, county, regional, and national scales.

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粪棚：促进美国农业中的养分循环利用

摘要 养分循环是可持续农业系统的基础，但很少有机制可以确保将动物饲养作业中剩余的粪便养分输送到营养不足的农田上使用。因此，粪便养分集中在可能威胁环境健康并使作为肥料资源的粪便贬值的地方。这项研究提出了“粪棚”的概念——动物饲养场周围的土地，粪肥养分可以重新分配到这些土地上，以满足环境、生产和经济目标。粪棚可以在多个尺度上进行管理，例如，在有动物和农作物的农场，在一个县内的动物农场和农作物农场之间，甚至在遥远的县的动物农场和农作物农场之间。以县际再分配为重点，我们根据它们从有限的牲畜生产（“来源”）中供应粪肥磷（P）和氮（N）或通过作物同化和去除多余的 P 和 N（“汇”）的能力对美国本土的 3109 个县进行了分类。 ）。在 48 个州中的 40 个州确定了粪便营养源县，其中大量集中在美国南部。粪肥 P 的源县数量大大超过粪肥 N 的源县（390 对 100），100 个粪肥 N 源县中有 99 个也是粪肥 P 的源县。相反，粪肥 N 的汇县数量超过粪肥 P 的汇县（ 2766 对 2317）。我们使用源县和汇县的 P 平衡来描绘四个由封闭养猪、家禽、乳制品和牛肉产业的各种组合主导的粪肥场。